Program being stopped while reading information

[Jmromeroes]

Program being stopped while reading information
Hello, I'm kind of new in C++ programming. I'm trying to create a
circular linked list with information the user enter, to solve the Josephus Problem, but I get an error and I don't know why. I've tried some solutions but I couldn't fix anything.
I would be very thankful if someone helps me.

 #include <iostream>
#include <stdlib.h>
#include <stdio.h>
#include <string>
#define locate (struct node*)malloc(sizeof(struct node))
#define compare(stri1, stri2) (stri1 == stri2? true:false)
using namespace std;
#define text(name) cin>>name
#define p1(stri) cout<<stri



struct node
{
	string name;
	struct node* next;
};

void insertNodeAtEnd(struct node** head, string name_n)
{	
	struct node* new_n, *q;
	
	new_n = locate;
	new_n ->name = name_n;
	q = *head;
	if(*head == NULL){
		new_n -> next = new_n;
		*head = new_n;
	}else{
		while(q->next != *head)
		{
		q = q->next;
		q->next = new_n;
		new_n -> next = (*head);
		}
	}
	
	
}

int main()
{  
	void createList(struct node**);
	void writeCircularList(struct node*);
	struct node* head;
	head = NULL;
	createList(&head);
	writeCircularList(head);
}

void createList(struct node** head)
{	
	string name;
	
	printf("Write the first soldier's name: \n");
	text(name);	
	while(!compare(name, "end"))
	{	
		insertNodeAtEnd(&(*head), name);	
		printf("Write another soldier's name: \n");
		text(name);
	}
		
}


void writeCircularList(struct node* head)
{	
	struct node* q;
	q = head;
	
	do{	
		p1(q->name);
		q = q->next;
	}while(q != head);	
}

Again, Thanks a lot! I don't really know what am I doing wrong. This is my very first question and I'm kind of interested.

[tipaye]

You have a struct node that has a member called name, which is of type string. When you do the malloc on line 23 (via evil macro locate), what you end up with is a block of raw, un-initialised memory.

struct node has no constructor to initialise its members, so you don't actually have a proper string object in your variable called name. You've got a bunch of random memory, and told the compiler it's a string. When the compiler tries to treat it as a string, probably by calling operator=() in line 24, all hell breaks loose.

If you had used operator new instead of malloc, the string constructor would have been called, a proper string object created, and the program would have gotten further, i.e. not crash, but it still wouldn't do what you want, because of a problem in insertNodeAtEnd().

You've really got a mixture of styles going on here, from the dodgy include statements, to the completely superfluous macros and the admixture of io solutions, just saying.

I know this isn't what you asked for, but I've made the code a little bit more C++ friendly. The only logic change I made was the while block at line 30, have a look:

#include <iostream>
#include <string>

using namespace std;

struct node
{
    string name;
    struct node* next;
};

void createList(struct node**);
void writeCircularList(struct node*);
void insertNodeAtEnd(node** head, string name_n);

int main()
{
    node* head = 0;
    createList(&head);
    writeCircularList(head);
}

void createList(node** head)
{
    string name;
   
    cout << "Write the first soldier's name:" << endl;
    cin >> name;
    while(name != "end")
    {
        insertNodeAtEnd(head, name);
        cout << "Write another soldier's name:" << endl;
        cin >> name;
    }
}

void writeCircularList(node* head)
{
    node* q = head;
    
    do
    {
        cout << q->name << endl;
        q = q->next;
    }
    while(q != head);
}

void insertNodeAtEnd(node** head, string name_n)
{
    node *q = *head;
    node *new_n = new node;
    new_n->name = name_n;
    if(*head == 0)
    {
        new_n->next = new_n;
        *head = new_n;
    }
    else
    {
        while(q->next != *head)
        {
            q = q->next;
        }
        
        q->next = new_n;
        new_n->next = *head;
    }
}

[Jmromeroes]

Oh man, thank you so much for that awesome reply! You answered even the questions I had but didn't ask. Thank you. It worked pefectly!